3,312 research outputs found
Phase-Coherent Transport through a Mesoscopic System: A New Probe of Non-Fermi-Liquid Behavior
A novel chiral interferometer is proposed that allows for a direct
measurement of the phase of the transmission coefficient for transport through
a variety of mesoscopic structures in a strong magnetic field. The effects of
electron-electron interaction on this phase is investigated with the use of
finite-size bosonization techniques combined with perturbation theory
resummation. New non-Fermi-liquid phenomena are predicted in the FQHE regime
that may be used to distinguish experimentally between Luttinger and Fermi
liquids.Comment: 4 pages, 3 figures, Revte
Reentrant spin glass behavior in a layered manganite La1.2Sr1.8Mn2O7 single crystals
We report here a detailed study of AC/DC magnetization and
longitudinal/transverse transport properties of
LaSrMnO single crystals below = 121 K. We
find that the resistivity upturn below 40 K is related to the reentrant spin
glass phase at the same temperature, accompanied by additional anomalous Hall
effects. The carrier concentration from the ordinary Hall effects remains
constant during the transition and is close to the nominal doping level (0.4
holes/Mn). The spin glass behavior comes from the competition between
ferromagnetic double exchange and antiferromagnetic superexchange interactions,
which leads to phase separation, i.e. a mixture of ferromagnetic and
antiferromagnetic clusters, representing the canted antiferromagnetic state.Comment: 5 pages, 5 figures, submitted to Phys. Rev.
Targeting of proteins to the twin-arginine translocation pathway
The twin-arginine protein transport (Tat pathway) is found in prokaryotes and plant organelles and transports folded proteins across membranes. Targeting of substrates to the Tat system is mediated by the presence of an N-terminal signal sequence containing a highly conserved twin-arginine motif. The Tat machinery comprises membrane proteins from the TatA and TatC families. Assembly of the Tat translocon is dynamic and is triggered by the interaction of a Tat substrate with the Tat receptor complex. This review will summarise recent advances in our understanding of Tat transport, focusing in particular on the roles played by Tat signal peptides in protein targeting and translocation. [Abstract copyright: © 2020 John Wiley & Sons Ltd.
Superconducting Qubits Coupled to Nanoelectromechanical Resonators: An Architecture for Solid-State Quantum Information Processing
We describe the design for a scalable, solid-state
quantum-information-processing architecture based on the integration of
GHz-frequency nanomechanical resonators with Josephson tunnel junctions, which
has the potential for demonstrating a variety of single- and multi-qubit
operations critical to quantum computation. The computational qubits are
eigenstates of large-area, current-biased Josephson junctions, manipulated and
measured using strobed external circuitry. Two or more of these phase qubits
are capacitively coupled to a high-quality-factor piezoelectric
nanoelectromechanical disk resonator, which forms the backbone of our
architecture, and which enables coherent coupling of the qubits. The integrated
system is analogous to one or more few-level atoms (the Josephson junction
qubits) in an electromagnetic cavity (the nanomechanical resonator). However,
unlike existing approaches using atoms in electromagnetic cavities, here we can
individually tune the level spacing of the ``atoms'' and control their
``electromagnetic'' interaction strength. We show theoretically that quantum
states prepared in a Josephson junction can be passed to the nanomechanical
resonator and stored there, and then can be passed back to the original
junction or transferred to another with high fidelity. The resonator can also
be used to produce maximally entangled Bell states between a pair of Josephson
junctions. Many such junction-resonator complexes can assembled in a
hub-and-spoke layout, resulting in a large-scale quantum circuit. Our proposed
architecture combines desirable features of both solid-state and cavity quantum
electrodynamics approaches, and could make quantum information processing
possible in a scalable, solid-state environment.Comment: 20 pages, 14 separate low-resolution jpeg figure
Earth matter density uncertainty in atmospheric neutrino oscillations
That muon neutrinos oscillating into the mixture of tau neutrinos
and sterile neutrinos has been studied to explain the
atmospheric disappearance. In this scenario, the effect of Earth
matter is a key to determine the fraction of . Considering that the
Earth matter density has uncertainty and this uncertainty has significant
effects in some neutrino oscillation cases, such as the CP violation in very
long baseline neutrino oscillations and the day-night asymmetry for solar
neutrinos, we study the effects caused by this uncertainty in the above
atmospheric oscillation scenario. We find that this uncertainty
seems to have no significant effects and that the previous fitting results need
not to be modified fortunately.Comment: 7 pages, 1 figure, to appear in Phys. Rev.
Excerpts from the paper: Research Status and Recommendation from the Alaska Workshop on Gravity Waves and Turbulence in the Middle Atmosphere, part 1.3A
Internal gravity waves are disturbances whose intrinsic frequencies k(c - u) are smaller than the Brunt-Vaisala frequency (N). Their importance arises because: they are the major components of the total flow and temperature variability fields of the mesosphere (i.e., shears and lapse rates) and hence constitute the likely sources of turbulence; and they are associated with fluxes of momentum that communicate stresses over large distances. For example, gravity waves exert a drag on the flow in the upper mesosphere. However, in order for gravity waves to exert a net drag on the atmosphere, they must be attenuated. There are two general types of processes that seek to attenuate gravity waves: dissipation and saturation. Dissipation is any process that is effective independent of the wave amplitude, while saturation occurs when certain wave amplitude conditions are met. Radiative damping is an example of dissipation, while convective overturning is an example of saturation. The two processes are not mutually exclusive
Universal Equilibrium Currents in the Quantum Hall Fluid
The equilibrium current distribution in a quantum Hall fluid that is
subjected to a slowly varying confining potential is shown to generally consist
of strips or channels of current, which alternate in direction, and which have
universal integrated strengths. A measurement of these currents would yield
direct independent measurements of the proper quasiparticle and quasihole
energies in the fractional quantum Hall states.Comment: 4 pages, Revte
Satellite observation and mapping of wintertime ozone variability in the lower stratosphere
Comparison is made between 30 mbar ozone fields that are generated by a transport chemistry model utilizing the winds from the Goddard Space Flight Center stratospheric data assimilation system (STRATAN), observations from the LIMS instrument on Nimbus-7, and the ozone fields that result from 'flying a mathematical simulation of LIMS observations through the transport chemistry model ozone fields. The modeled ozone fields were found to resemble the LIMS observations, but the model fields show much more temporal and spatial structure than do the LIMS observations. The 'satellite mapped' model results resemble the LIMS observations much more closely. These results are very consistent with the earlier discussions of satellite space-time sampling by Salby
Infrared catastrophe and tunneling into strongly correlated electron systems: Exact solution of the x-ray edge limit for the 1D electron gas and 2D Hall fluid
In previous work we have proposed that the non-Fermi-liquid spectral
properties in a variety of low-dimensional and strongly correlated electron
systems are caused by the infrared catastrophe, and we used an exact functional
integral representation for the interacting Green's function to map the
tunneling problem onto the x-ray edge problem, plus corrections. The
corrections are caused by the recoil of the tunneling particle, and, in systems
where the method is applicable, are not expected to change the qualitative form
of the tunneling density of states (DOS). Qualitatively correct results were
obtained for the DOS of the 1D electron gas and 2D Hall fluid when the
corrections to the x-ray edge limit were neglected and when the corresponding
Nozieres-De Dominicis integral equations were solved by resummation of a
divergent perturbation series. Here we reexamine the x-ray edge limit for these
two models by solving these integral equations exactly, finding the expected
modifications of the DOS exponent in the 1D case but finding no changes in the
DOS of the 2D Hall fluid with short-range interaction. We also provide, for the
first time, an exact solution of the Nozieres-De Dominicis equation for the 2D
electron gas in the lowest Landau level.Comment: 6 pages, Revte
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